The Ottawa River, also known as Ottawa Creek, is a short river, approximately 15 mi (24 km) long (or about 45 mi (72.5 km if the longest tributary is included), in northwest Ohio and southeast Michigan in the United States. It drains an area on the Ohio-Michigan border along the eastern and northern fringes of the city of Toledo, goes through Ottawa Hills, and empties directly into Lake Erie. It is one of two rivers in northwestern Ohio that share the same name, along with Ottawa River that is a tributary of the Auglaize River. The upper 4 mi (6 km) of the river in Michigan north of Sylvania, Ohio is sometimes called North Tenmile Creek, while another branch rising in Fulton County, Ohio, is called Tenmile Creek.
It rises in extreme Southeastern Michigan, southwest of Ottawa Lake, approximately 3 mi (5 km) north of the Ohio-Michigan state line. It flows south across the state line to Sylvania, approximately 5 mi (8 km) northwest of Toledo, then flows southeast into western Toledo, where it turns aburptly northeast. For its lower 5 mi (8 km) it flows along the north side of Toledo roughly parallel to the Maumee River separated from it by approximately 2 mi (3 km). It crosses the Michigan state line for its lower 1 mi (1.6 km), entering Little Maumee Bay on Lake Erie.
The Ottawa River Risk Assessment, a report published in 2000, tested the water of the lower section of the Ottawa River, and found many chemicals in the water with an hazard quotient greater than 1 (from highest to lowest concentration): lead, aluminum, PCBs, manganese, iron, DDT, thallium, selenium, chromium, nickel, cadmium, cyanide, and zinc.
The reasons for the poor water quality are primarily its form and structure, since it has a slow flow, and, secondly, runoff and discharge from landfills and sewers. The City of Toledo has made it a priority to clean up the river, and action has been taken to clear landfills and tributaries.